Grease filling arrangement in a cutter for a boring head

ABSTRACT

An arrangement for replenishing lubricating grease in drill cutters ( 3 ) that include a conical outer barrel ( 7 ) which is rotatable about a shaft ( 5 ) disposed centrally in the cutter, wherein there is provided in the cutter shaft ( 5 ) a passageway ( 16 ) that extends along the shaft from the cutter end of largest diameter and that connects with a transverse passageway ( 18 ) which opens into a bearing-accommodating space ( 13 ) in the cutter for delivering lubricating grease to the space ( 13 ), and wherein a lubricating nipple ( 19 ) is provided on the cutter end wall of largest diameter and functions to allow lubricating grease to be released from the bearing-accommodating space ( 13 ).

The present invention relates to an arrangement pertaining to thereplenishment of drill cutters with lubricating grease, and thenparticularly such cutters as those that are used in drilling bits forraise drilling.

A reamer is a drill bit that is normally drawn up through a predrilledhole by means of a rod extending in the hole. The reamer includes acarrier to whose upper side there is attached a drilling tool in theform of a number of so-called cutters. These cutters rotate against therock surface, or stone surface, with which they are in abutment, as thereamer rotates in response to rotation of the rod. The cutters have afrusto-conical shape and are mounted with the largest diameter facingoutwards, i.e. away from the rod disposed centrally in said carrier. Thecutters are mounted on shafts accommodated in the attachments carried onthe upper side of the carrier, with the axes of respective cuttersextending mainly radially to the rod.

In turn, the cutters are provided with bearings by means of which thecutters are able to rotate about their respective axes. These bearingsand also the seals between cutter and cutter shaft are kept lubricatedwith grease fed into the cutter interior. A shaft is usually filled withlubricating grease, by injecting the grease through a nipple at one endof the shaft and allowing the grease to flow out through a nipple holeon the other end of said shaft. This method functions very effectivelyprovided that the cutter is not mounted within the reamer. However, whenit becomes necessary to replenish or change the grease, which must doneoften when underground conditions are troublesome, it is difficult toreach the nipple seated at the narrower end of the cutter facing inwardstowards the rod.

Accordingly, an object of the present invention is to provide a novelarrangement for refilling drill hole cutters of the aforesaid kind withlubricating grease.

This object is achieved with an arrangement according to the presentinvention in which there is provided a passageway which extends alongthe shaft from the cutter end of largest diameter and which communicateswith a transverse passageway that opens into the space accommodating acutter bearing, for the supply of lubricating grease to said space, andin which there is provided in the cutter wall of largest diameter alubricating nipple that functions to allow lubricating grease to exitfrom said bearing accommodating space.

The invention will now be described in more detail with reference to anon-limiting embodiment thereof and also with reference to theaccompanying drawings, in which

FIG. 1 is a schematic perspective view of part of a reamer having anumber of cutters;

FIG. 2 is a perspective view of a cutter; and

FIG. 3 is a longitudinally sectioned view of a cutter.

Shown in FIG. 1 is part of a reamer that includes a carrier 1 which issupported by a rotatable rod 2. The carrier 1 has disposed on its upperside a number of cutters 3, in the illustrated case four such cutters.The cutters 3 are mounted in fasteners 4 provided on the carrier, withthe cutter shafts 5 fitted in the fasteners 4. As will be seen, thecutters 3 have a frusto-conical shape with the narrower end 6 of thecutters facing inwards towards the rod 2 mounted centrally in thecarrier 1. The cutter shafts 5 are fixedly mounted in the fasteners. Inother words, the cutter shafts 5 are not rotatable in the fasteners 4,but that the conical outer barrel 7 of the cutters 3 is able to rotateabout the shaft 5 disposed centrally in the cutter. The cutter hasdisposed about its outer barrel surface a number of inserts 8 made, forinstance, of tungsten carbide and functioning to cut the rock or stonein a drilling operation.

The outer barrel 7 of respective cutters 3 is subjected to largestresses and strains and is rotatably mounted on the shaft 5 by means ofstrong bearings 9, 10. Fitted to both end walls of the barrel 7 are wallelements 11, 12 which seal between the barrel 7 and the shaft 5. Thereis formed in this way an internally closed space 13 which accommodatesthe bearings 9, 10 and also end seals 14, 15. The internal space 13 isnormally filled with grease for lubrication of the bearings 9, 10. Thewall elements 11, 12 are sealed against the barrel 7 and the shaft 5 bymeans of end seals 14, 15 that include slip seals and O-rings.

According to the present invention, lubricating grease is delivered tothe bearing accommodating space 13 of the cutter through alongitudinally extending passageway 16, which extends centrally in theshaft 5 from that end of the cutter which has the largest diameter. Afilling nipple 17 is provided at this end of the shaft, such as toenable grease to be delivered to said bearing space with the aid of atypical grease gun. The passageway 16 extends from said cutter end to aposition beyond the innermost bearing 9 as seen from said end. Thepassageway 16 communicates at this position with a transverse passageway18 which opens into the bearing-accommodating space 13 beyond theinnermost bearing 9. Also provided in the end wall 12 of the cutter is adrainage nipple 19 through which old lubricating grease can be drainedfrom the cutter interior when replacing the old grease with freshgrease. The same end wall 12 will also preferably include anoverpressure valve 20 which opens automatically should the pressure inthe internal space 13 of the cutter become excessively high, therewithreleasing grease from said space.

The transverse passageway 18 is preferably provided in a stress-neutralregion of the shaft, particularly so that the outlet of the transversepassageway 18 into the cutter lies in a stress-neutral region. The forcearrow 21 shown in FIG. 3 indicates the normal force flow, wherewith thetransverse passageway 18 is disposed generally at right angles to theline of action of the main force.

In the case of the illustrated embodiment, the transverse passageway 18extends at right angles in both directions from the passageway 16provided in the shaft 5. This is a preferred feature of the invention,since it is then possible to deliver grease to two diametrically locatedpositions of the shaft 5 within the inner space 13 of the cutter,therewith ensuring more positively that the entire space 13 will befilled with grease.

However, the transverse passageway may extend in only one directionessentially radially outwards from the longitudinally extendingpassageway 16. Alternatively, the transverse passageway may beorientated to extend generally at right angles to the line of attack ofthe main force.

In practice, the transverse passageway 18 is orientated so that it willlie generally horizontal when the cutter is fitted in its position ofuse on a reamer. As the reamer is used, the direction of attack of themain force will be generally vertical, since the reamer is drawn upthrough a predrilled vertical hole or bore.

The arrangement of the lubricating passageways 16, 18 in accordance withthe invention ensures that all bearings in the cutter 3 will be properlylubricated, so as to avoid damage to the bearings, despite the fact thatlubricating grease is delivered from the same end as that from which oldand spent grease shall flow out. Despite this, the bearing-greasereplenishing nipple 17 may be provided in the larger end wall of thecutter distal from the rod seated centrally in the reamer, so that easyaccess can be had to both the refilling nipple 17 and the drainagenipple 19.

1. An arrangement for replenishing lubricating grease in drill cutters (3) that include a conical outer barrel (7) which cutter is rotatable about a shaft (5) disposed centrally in the cutter, characterised by a filling lubricating nipple (19) provided in the cutter shaft (5) on the cutter end wall of largest diameter and opening into a passageway (16) that extends longitudinally in the cutter shaft (5) and that connects with a transverse passageway (18) which opens out into a bearing-accommodating space (13) in said cutter (3), for delivering lubricating grease to said bearing-accommodating space (13) at a position beyond the innermost bearing (9) of bearings (9, 10) disposed between the outer barrel (7) of the cutter and the shaft (5) as seen from the cutter end of largest diameter; and by a lubricating nipple (19) provided on the same cutter end wall as said filling lubricating nipple (17) and functioning to allow lubricating grease to be released from said bearing-accommodating space (13).
 2. An arrangement according to claim 1, characterised in that the longitudinally extending passageway (16) is disposed centrally in the cutter shaft (5).
 3. An arrangement according to claim 1, characterised in that the transverse passageway is located in a stress-neutral region of the cutter shaft (5).
 4. An arrangement according to claim 3, characterised in that the transverse passageway (18) is orientated generally horizontally when the cutter is mounted on a reamer in its position of use.
 5. An arrangement according to claim 1, characterised in that the transverse passageway (18) extends generally radially out from the longitudinally extending passageway (16).
 6. An arrangement according to claim 1, characterised in that the transverse passageway (18) extends out in generally opposite directions from the longitudinally extending passageway (16) and opens out at two diametrically opposite places on the shaft (5).
 7. (canceled)
 8. An arrangement according to claim 2, characterised in that the transverse passageway is located in a stress-neutral region of the cutter shaft (5). 